This invention relates to an apparatus for restricting discharge of evaporated fuel gas, the apparatus having such a construction that gas evaporated in a fuel tank to be mounted on a vehicle is introduced into a canister for adsorbing the gas therein.
As a conventional apparatus of this kind, there is known an apparatus, as shown in FIG. 4, in which a fuel tank a and a canister b are connected together via a two-way valve c. The two-way valve c operates to open when the internal pressure in the fuel tank a has reached a predetermined positive set pressure, whereby the evaporated gas inside the fuel tank a is introduced into the canister c, and operates to open when the internal pressure in the fuel tank a has lowered to a predetermined negative pressure, whereby the evaporated gas kept stored in the canister c is returned to the fuel tank a.
The evaporated gas inside the fuel tank a is not introduced into the canister c until the pressure of the evaporated gas has increased to the positive set pressure. It follows that there is a possibility that the evaporated gas is discharged into atmosphere at the time of filling the fuel tank with a fuel, or the like. As one way of coping with this possibility, it is considered to connect, in parallel with the two-way valve c, a solenoid valve d which opens at the time of opening a filler lid of the fuel tank or the like. In this arrangement, even if the internal pressure in the fuel tank is below the set pressure, the evaporated gas can be introduced into the canister b through the solenoid valve d, thereby preventing the evaporated gas from being discharged into atmosphere.
In case the solenoid valve d is provided as described above, the arrangement will be that three-way joints e are provided on both sides of the two-way valve c so that the solenoid valve d is connected in parallel with the two-way valve c via tubes f between both joints e. In this arrangement, however, the piping work in the step of vehicle assembling work becomes troublesome. Further, the number of piping connections increases with a consequent increased possibility of leaks of the evaporated gas from these piping connections. There is also required a large space for disposing the two valves, resulting in a poor space-efficiency.